Question

Which of the following dopant is NOT used in Ge to obtain n-type semiconductor?

• A. P
• B. As
• C. Sb
• D. B

Hint:

N-type doping uses group 15 elements with five valence electrons, while boron gives a p-type semiconductor.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Germanium is in group 14 with four valence electrons. Doping adds a small amount of another element. A group 15 dopant has an extra electron, giving an n-type semiconductor.

Step 2: Detailed Explanation:
Phosphorus (P), arsenic (As) and antimony (Sb) are all group 15 elements with 5 valence electrons. Each uses 4 to bond with Ge and leaves one free electron. This makes n-type material.
Boron (B) is group 13 with 3 valence electrons. It leaves a missing electron, called a hole, so it makes a p-type semiconductor.

Step 3: Pick the odd one.
P, As and Sb are valid n-type dopants. Boron is not.

Final Answer:
Boron is not used for n-type doping, option (D). \[ \boxed{\text{B}} \]